Furnace with flue gas sampler



May 25, 1965 J. v. HYND FURNACE wITH FLUE GAS SAMPLER 2 Sheets-Sheet 2 Filed April 8, 1963 INVENTOR. JAMES V. HYND ATTORNEYS.

United States Patent O 3,185,456 FURNACE WITH FLUE GAS SAMPLER James V. Hynd, Southgate, Mich., assigner to National Steel Corporation, a corporation of Delaware Filed Aug. 8, 1963, Ser. No. 300,752 Claims. (Cl. 263-15) The present invention relates to furnace construction of the type including a flue gas sampler for withdrawing a sample of gas from the interior of the furnace and conveying it to a gas analyzer to determine whether the gas leaving the metal treating zone -of the furnace is of the desired composition. The present invention has utility in such furnaces that are provided with a lance of a burner for conveying a uid into the furnace toward the metal treating zone, whether that fluid is in liquid or Vapor phase and Whether or` not it is a combustible fluid.

The invention has particular utility, and will be illustrated by way of example, in connection with open hearth furnaces of the regenerative type in which burners or lances extend through opposite end walls and are fired alternately. Such regenerative furnaces make use of the exiting ue gases for purposes of transferring heat to the entering gases lby regenerative heat exchange. As the burner at one end of the furnace is firing, ue gases will leave the other end of the furnace and pass over regenerative heat exchange bodies or checkers comprised of refractory brick stacked so as to permit the ow of gas among them. When the checkers are suiciently heated, the firing is discontinued from the one burner and is initiated from the other burner, with the result that the furnace then res in the opposite direction and the tiue gases leave the furnace in the opposite direction and heat up a second mass of checkers or brick work. At least a portion of the make-up gas for tiring in this second direction is drawn in over the previously heated checkers, which give off their heat to the entering gases while the second body of checkers is being heated. In this way, a substantial proportion of the heat of the furnace never gets beyond the checkers but is simply returned to the furnace in the entering gas.

In order to study the condition of the melt in the furnace, thereby to regulate the quantity or nature of the fluid lbeing being fed to the metal treating zone and/or to determine the end point of the heat, it is desirable to Withdraw and analyze samples of the flue gas immediately it leaves the surface of the bath. However, it has been extremely diicult to do so in the past, for a number of reasons. In the first place, the results were erratic and the analyses of this withdrawn gas were subject to such great variation as to cast doubt on the representative nature of the samples being obtained. In the second place, the equipment was quite expensive inasmuch as it was necessary to insert into the furnace a probe for catching a sample of the gas, and to water-cool the probe so that the probe would not be adversely affected by the high heat of fthe furnace. In the third place, such probes as were known heretofore were subject to such rapid fouling from the slag and other entrained liquid and solid impurities in the flue gas that the sampling probes Ihad to be removed and cleaned or replaced at very short intervals and accordingly could not be relied on to withdraw an indicative sample at any particular time in the heat.

Although a number of attempts have been made to overcome the above and other diculties and disadvantages in this art, none, as far as it is known, were entirely successful when practiced commercially on an industrial scale.

Accordingly, it is an object of the present invention to 3,185,456 Patented May 25, 1965 ice provide furnace construction in which means are provided for quickly and easily withdrawing an indicative sample of the Hue gas from the furnace.

Another object of the present invention is the provision of a fiue gas sampler adapted quickly and easily to withdraw an indicative uid sample from the interior of a furnace.

Finally, it is an object of the present invention to provide a flue gas sampler and furnace construction embodying that sampler, Which will be relatively simple and inexpensive to manufacture, easy to install, maintain an operate, and rugged and durable in use.

Other objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompany ing drawings, in which:

FIGURE 1 is a side cross-sectional View, somewhat diagrammatic in nature and with parts broken away, of an open hearth furnace embodying tlue gas samplers according to the present invention;

FIGURE 2 is a reduced plan View of the structure of FIGURE l with parts broken away for clarity;

FIGURE 3 is a right side view of the structure of FIGURE 2;

FIGURE 4 is an enlarged elevational view, with the casing in cross section but with the conduits within the casing substantially intact, and with parts broken away, of an end Iwall burner according to the present invention;

FIGURE 5 is a cross-sectional end view of apparatus according to the present invention, taken along the line 5-5 of FIGURE 4; and

FIGURE 6 is an enlarged view of a portion of FIG- URE 4, with parts broken away for clarity, showing a preferred form and arrangement of the intake end of a sampler conduit according to the present invention.

Referring now to the drawings in greater detail, there is shown in FIGURES 1, 2 and 3 an open hearth furnace comprising the usual hearth 1 and roof 3, with a backwall 5 and a front wall 7. Front wall 7 has a plurality of doors 9 therethrough for the reception of charge and scrap and the like from a charging vehicle that rides on charging floor 11.

At the opposite ends of the furnace are located ports 13 through which the ue gases move in alternately opposite directions. Ports 13 are bounded endwise by end walls 15. The ue gases leaving the furnace at each end pass through slag pockets 17 in which a good bit of solid materials entrained in the rapidly moving flue gases are caught before the gases pass through the usual checkers 1g. Checkers 19, as explained above, are regenerative heat exchange means comprising bricks with open spaces between them, so that the relatively hot flue gases and the relatively cold feed gases passing in opposite directions through checkers 19 will alternately give up heat to the checkers and remove heat from the checkers, respectively. The relatively cool flue gases, after giving up their heat to checkers 19, leave through tlues 21, which also provide entry for the relatively cold feed gases.

The metallic charge to be treated in the furnace is shown in EIGURE l in the form of a bath 23 of molten iron undergoing melt-down or refining or other heat treating operation in the furnace. To supply the heat to the furnace, end wall burners 2S are provided that extend one through each end wall 15. Burners 25 are generally downwardly inclined as seen in FIGURE 1 and bridge across port 13, so that the flue gases leaving the furnace and the heated gases entering the furnace pass about burners 25. As also explained above, burners 25 are directed generally toward each other and fire only alternately. In FIGURE 1, the right burner 25 is shown as the tiring burner, while the left burner A25 is idle.

The structure of each burner Z is indicated in FIG- URES 4, 5 and 6. Each burner comprises a generally cylindrical hollow casing 27 closed at both ends. A central conduit 29 for oil or other liquid fuel extends coaxially through casing 27, and gas conduits 3l and 33 extend through casing 27 parallel to the axis of the casing and to central conduit 29 and to each other. One of conduits 31 and 33 might for example be for conveying oxygen toward the combustion area, while another of the conduits 31 and 33 might for example be for the purpose of conveying fuel gas toward the combustion area. Of course, other fluids instead of or in addition to these may be fed through these conduits, such as steam or air, and solid fuel such as powdered coke or liquid fuels other than oil may also be fed to the combustion area.

In any event, conduits 29, 31 and 33 converge adjacent the discharge end 35 of burner 25 and all feed into a nozzle 37 in which the various fluids are mixed and from which the mixture emerges as a combustible mixture at a velocity preferably above the flame propagation velocity of the mixture, so that the flame does not backfire into nozzle 37. Of course, the various fluids emerging from conduits 29, 31 and 33 into nozzle 37 have a venturi or eductor effect on each other so as to promote the flow of the various fluids.

Also disposed within and extending longitudinally of casing 27 is a pair of cooling water conduits 39 and 41 that terminate within casing 27 adjacent discharge end 35. Conduits 39 and 41 are preferably spaced apart a substantial distance diametrically on opposite sides of the axis of the burner so as to introduce cooling water into the burner at widely spaced points, thereby to assure a uniform cooling of all parts of the burner. A cooling water outlet 43 adjacent the rear end of the burner removes the used cooling water. As is conventional in burners and lances employing cooling water conduits, the water is at its coolest where it emerges from the ends of conduits 39 and 41 adjacent discharge end 35, which is also ordinarily the hottest part of the burner. Therefore, the coolest water is supplied to the point at which it is most needed, the warmest water being removed from the burner adjacent the rear end where it is the least needed for cooling purposes.

As thus far described, the structure and function of the furance construction and burner structure may be quite conventional.

A unique feature of the present invention is the provision of a flue gas conduit 45 that extends a substantial distance through the interior of casing 27. It will be obvious that casing 27 is in effect a water jacket about the conduits 29, 31 and 33; and the addition of flue gas conduit 45 to this assembly of other fluid conduits take advantage of the cooling water within casing 27, but without adding appreciably to the refrigeration that must be provided by means of the cooling water.

Flue gas conduit 45 lterminates at an intake end 47 which is disposed beneath the associated burner Z5. Intake end 47 is disposed closely adjacent the underside of casing 27 and draws flue gas samples from a region closely adjacent the underside of casing 27. It should be noted that intake end 47 is turned away from the direction of approach of the flue gases, as can be seen in FIGURE l. Specifically, intake end 47 opens downwardly; and in the sense that the underside of casing 2'7 of each burner 25 faces away from the opposite burner 25, intake end 47 opens away from the opposite burner 25. Therefore, although intake end 47 opens generally downwardly, the downward inclination of burner assures that intake end 47 will open somewhat toward the associated end wall 15. Preferably, intake end 47 is flush with the underside of casing 2.7, thereby to achieve maximum cooling of intake end 47. With intake end 47 thus disposed, it has been found that a minimum of solid or other foreign material is inducted into flue gas conduit 45. It

Cil

is accordingly much less frequently necessary, if ever necessary, to pull the flue gas sampling equipment to clear it of solid encrustation as was true in the prior art.

Flue gas conduit 45 in the illustrated embodiment is shown as a length of straight metal tubing extending diagonally through each burner 2.5 and terminating at its upper rear end above an upper rear portion of the associated burner 25 outside the furnace. It will of course also be apparent that instead of this configuration of flue gas conduit 45, conduit 45 could terminate at its intake end in about the position seen around the middle of FIG- URE 4, but toward its rear end be parallel to conduits 29, 31 and 33 and extend through the rear end wall of casing 27 along with those other three fluid conduits. In this case, of course, conduit 45 would not be straight.

In either event, flue gas conduit 45 terminates at its rear end in a coupling 49 by which it is detachably connected with a relatively flexible conduit 51 which communicates with a flue gas analyzer 53. `In FIGURE l, for purposes of illustration, two analyzers 53 have been shown. It will of course be understood, however, that in a preferred embodiment there would only be one analyzer 53 that receives flue gas samples alternately from both conduits 45. The particularV construction and operation of the analyzer 53 and its gas feed means is quite conventional and need not be described here.

It will of course be understood that, like the end wall burners, the flue gas conduits 45 operate only alternately, in that the conduit 45 opposite the firing burner 25 will be receiving flue gas samples; and that upon reversing of the firing of the end wall burners, the flue gas sampling conduits 45 will reverse and the other conduit 45 will receive the samples to pass to the analyzer 53. Conventional means for placing each flue gas conduit 45 alternately in fluid circuit with the analyzer 53 are preferably provided, as well as conventional means for purging the flue gas conduits 45 as by the passage of steam in a reverse direction to leave through end 47 of conduit 45.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention as defined by the appended claims.

What is claimed is:

l. In a furnace, means for conveying a fluid from outside the furnace into the furnace, said means being elongated in the direction of fluid movement and having an external water jacket defining a water space about said means to cool said means, means extending through said water space within the jacket and communicating with the furnace atmosphere closely adjacent the jacket for withdrawing samples of furnace atmosphere and for conveying the samples to outside the furnace for analysis; and a flue gas analyzer outside said furnace in communication with the last-named means.

2. Apparatus as claimed in claim l, the last-named means terminating closely adjacent the jacket.

3. Apparatus as claimed in claim l, the last-named means terminating substantially flush with the jacket.

4. Apparatus as claimed in claim l, said means for conveying a fluid extending generally downwardly from a horizontal plane, said external water jacket having a topside and an underside; and said means extending through said water space within the jacket terminating on the underside of the jacket.

5. In a regenerative furnace having alternately operating burners extending generally toward each other through generally vertical opposite parallel walls of the furnace and having regenerative heat exchange means for alternately withdrawing heat from exiting gases and giving up heat to entering gases, eac-h burner having means for conveying a uid from outside the furnace into the furnace, said means being elongated in the direction of fluid movement and having an external water jacket deining a water space'about said fluid conveying means to cool said fluid conveying means; the improvement comprisiug means extending through said water space within the jacket of a burner extending through each of said opposite walls and communicating with the furnace atmosphere closely adjacent the jacket for withdrawing samples of furnace atmosphere and for conveying the samples to outside the furnace for analysis, and a ue gas analyzer outside said furnace in communication with the last-named means.

6. Apparatus as claimed in claim 5, the last-named means terminating closely adjacent the jacket.

7. Apparatus as claimed in claim 5, the last-named means terminating substantially flush with the jacket.

8. Apparatus as claimed in claim 5, the last-named means comprising a conduit having an end within the 6 furnace that opens away from the burner of the opposite furnace wall.

9. Apparatus as claimed in claim 5, the last-named means comprising a conduit having an end within the furnace that opens downwardly and away from the burner of the opposite furnace wall.

10. Apparatus as claimed in claim 5, said means for conveying a fluid extending generallyv downwardly from a horizontal plane, said external water jacket having a topside and an underside; and vsaid means extending through said water space within the jacket terminating on the underside of the jacket.

CHARLES SUKALO, Primary Examiner.

JOHN I. CAMBY, Examiner. 

1. IN A FURNACE, MEANS FOR CONVEYING A FLUID FROM OUTSIDE THE FURNACE INTO THE FURNACE, SAID MEANS BEING ELONGATED IN THE DIRECTION OF FLUID MOVEMENT AND HAVING AN EXTERNAL WATER JACKET DEFINING A WATER SPACE ABOUT SAID MEANS TO COOL SAID MEANS, MEANS EXTENDING THROUGH SAID WATER SPACE WITHIN THE JACKET AND COMMUNICATING WITH THE FURNACE ATMOSPHERE CLOSELY ADJACENT THE JACKET FOR WITHDRAWING SAMPLES OF FURNACE ATMOSPHERE AND FOR CONVEYING THE SAMPLES TO OUTSIDE THE FURNACE FOR ANALYSIS; AND A FLUE GAS ANALYZER OUTSIDE SAID FURNACE IN COMMUNICATION WITH THE LAST-NAMED MEANS. 